Growth of vibrissae in the marsupial Trichosurus vulpecula

Abstract

The autoradiographic technique was used to study the growth of the vibrissae in the mystacial, genal, and supraorbital regions of three brush-tailed possums. During the first cycle there were well-marked gradients in length within and between the rows of mystacial vibrissae. The length growth rates of the corresponding vibrissae on the left and right sides of the body were almost identical at any particular time, although the growth rates varied throughout the cycle. The variations in the final lengths of the vibrissae were due to variations in both the growth rate and the length of the cycle. The diameters increased continuously throughout the cycle. The rate of regrowth after plucking vibrissae from active and resting follicles was also studied. The new vibrissa in a particular follicle initially grew at a much faster rate than either the corres- ponding undisturbed vibrissa on the other side of the head or the vibrissa which had just been plucked. The subsequent rate of growth decreased progressively throughout the cycle. In spite of differences in growth rates during the first and later cycles, the overall dimensions of the successive vibrissae from a particular follicle were very similar. The normal retention of vibrissae was studied in one animal. At least some vibrissae were retained for more than a year after they had stopped growing. The results demonstrate that the vibrissae of T. vulgecula provide an excellent model for studies of the factors controlling follicle activity.